This invention is related to apparatus for monitoring what a human subject is looking at and, more particularly, to a head-mounted device for detecting at least a portion of the field-of-view of its wearer.
A need exists in various fields to monitor what a person is looking at. For example, in the field of advertising, tests are conducted in which a number of items are placed in front of a subject in order to determine the one to which his attention will be directed. The items, for example, can be packages with each carrying a different design, juxtaposed pages of advertisements, or billboards. In the military field, such a device can be used in pilot training programs for the recording, and later analysis, of the pilot's actions. Also, if connected to a suitable control system, this device can be used to guide a missile all the way to its target by having the pilot merely look at it. In the field of sports, such a monitoring device can be used to analyze a participant's actions. For example, a batter in a slump may not be looking properly at the ball, or a quarterback may not be paying attention to key features of the defense in particular situations. This can be picked up with a device that detects what the player is viewing. These and other applications require a portable, small, light, head-mounted device which can be conveniently worn without interfering with vision or other activities.
Various head-mounted devices already exist which can monitor the view being looked at by the wearer. For example, U.S. Pat. No. 3,542,457 and the publication "Eye Movement Recorder" Series V-0165 by the Polymetric Company disclose view detectors carried by a headband. The publication "Behavior Research Methods & Instrumentation," 1975, Vol. 7(5), includes an article "Survey of Eye Movement Recording Methods," page 405, which shows a face mask and a headband carrying such a device. The same publication, on page 404, shows a helmet-mounted view detector. All of these approaches, however, have certain disadvantages. Helmet-mounted devices are relatively heavy and bulky and may cause tiredness and thus bring on lack of concentration. Also, they interfere somewhat with the wearer's vision. Furthermore, women resist wearing them because it can muss their hair. (One must keep in mind that in advertising testing, for example, the subjects are often volunteers picked at random on the street.) In addition, the helmet does not accomodate eye-glass wearers thus eliminating a large segment of the population from its use. The headband-mounted devices suffer from the same disadvantages as the helmet-mounted ones and, in addition, are difficult to keep in place on the head. If the band is tightened to make it more secure, the pressure may cause headaches. The face mask approach is awkward to wear, also needs to be tight in order to wear it securely which can cause discomfort, and many people perspire heavily under them.
In my U.S. patent application No. 486,031 filed Apr. 18, 1983, I discuss eyeglass-mounted view-monitoring devices. Those embodiments have certain advantages over the helmet-mounted type in being light, compact, and more convenient (at least for women, for example). Also, eyeglass wearers can be accomodated. However, since in that application the view-monitoring device is permanently attached to the frame, for each eyeglass wearer a set of lenses of suitable prescription must be inserted into the frame. This requires that an inventory of lenses be kept on hand. Also, since the frame is not the subject's own, some degree of discomfort during wear is to be expected.